The most common cause of death following portasystemic shunt in patients with cirrhosis and portal hypertension is liver failure. Liver failure not infrequently occurs following diversion of portal blood from the liver by the shunt. The relationship between preoperative portal vein blood flow and total hepatic blood flow and the clinical response to a given portasystemic shunt is not understood because of the lack of appropriate techniques for portal vein blood flow determination and the inherent difficulties with techniques of total hepatic blood flow determination in cirrhotic patients. Determination of pre-shunt portal vein blood flow is of particular importance at this time because of the recent development and application of newer types of hemodynamically different portasystemic decompressive procedures. Several recent technical advances now make pre- and post-shunt hemodynamic assessment feasible in the unanesthetized patient: (1). Direct portal flow determination by water-immiscible droplets instilled into the portal vein; (2). Demonstration of feasibility and safety of post-shunt as well as pre-shunt umbilical vein cannulation; (3). Feasibility of early post- operative portal flow study eliminating the necessity of prolonged umbilical vein catheterization which serves to eliminate the potential of catheter complications; (4). Demonstration of the safety of a new water-soluble contrast media (metrizamide) which has recently been found to possess the unique ability to form transient intravascular radiopaque droplets. This will allow complete assessment of hepatic blood supply by direct methods without interference of portasystemic collaterals for the first time. The relationship of preoperative and postoperative portal vein blood flow to post-operative morbidity (liver failure) and mortality is being studied in patients randomized into groups in which either mesocaval (Drapanas) interposition or selective distal splenorenal (Warren) shunt is performed.